Bicycles and cyclists have always been a part of traffic flow in North America and elsewhere around the world, even pre-dating the presence of motorized vehicles. Today, cyclists exist in traffic alongside motorists and have unique challenges for mobility within a city or highway transit environment.
For years, bicycle users have been challenged with how to indicate to a traffic signal that they are present so that they can obtain a green light. There are only a few ways for a cyclist to provide an indication to a traffic signal controller at a signalized intersection that it is present: the cyclist can press a pedestrian crosswalk or bicycle pushbutton, wait for a car to pull up in the same direction so that the car is detected and triggers the green light or, simply assume that detection has occurred.
When pushing a pedestrian pushbutton, often the cyclist has to dismount the bicycle in the roadway and step onto the sidewalk to access the crossing pushbutton. With a special bicycle crossing pushbutton, the cyclist can often stay on the bicycle and lean over to push the button. Depending on intersection geometry and configuration, the cyclist may have to unsafely cross a vehicle lane to access the pushbutton.
Cyclists often assume they have been detected and hope that a traffic light will turn green soon for them to pass through. If they do not get a green light and are ‘missed’ they will often determine that the only way to cross is to wait for an acceptable moment to cross against the red light. This can result in dangerous situations, such as near-misses and collisions, endangering safety of all users of the traffic intersection.
Traffic engineers and planners discourage the use of the pedestrian crossing for bicycle users, as the timing required for pedestrians to safely cross is far greater than that of a cyclist. This causes inefficiency in signal timing and can lead to higher congestion in busy periods, as well as frustration during quiet times as motorists wait for a green light when no traffic is present in the opposing signal phases and the cyclist has already passed through the crosswalk.
More recent advances in detection technology allow bicycles to be detected at intersections automatically, as has been done for years for motor vehicles. Examples of these types of detection include wired loops in the roadway, radar sensors, infrared sensors and video sensors. There are many new types of in-ground loop detectors that attempt to pick up the metal signature of a bicycle crossing over the loop. Different shapes (diamond, parallelogram) and sizes and sensitivities have been used with varying levels of success. However, with many new bicycles being made from non-metallic carbon fiber, this technology has faced increased challenges to accurately detect bicycles. Non-invasive technologies such as radar and video detection attempt to identify bicycles by their radar reflective signature or through the analysis of pixels in a digital video image. Both of these technologies can successfully detect bicycles of many different sizes, shapes and materials. In mixed-flow traffic, however, they can have difficulty in differentiating between motorcycles and bicycles. Thus the present array of techniques do not offer a single comprehensive solution to detection with a high degree of accuracy.
Therefore, despite advances in automatic detection, it remains that cyclists have no way of confidently knowing if their presence has been detected, and may continue to engage in dangerous intersection crossing behavior as a result.